The present invention relates to an improvement in a reciprocating fluid transfer pump in which a once, having flown into a fluid delivering chamber, is discharged therefrom by expanding and contracting a diaphragm disposed at an end portion of a center rod capable of making a reciprocating movement relative to a main body block and defining the fluid delivering chamber and a driving chamber.
In a reciprocating fluid transfer pump as described in U.S. Pat. No. 6,106,246, there has been used a diaphragm-type pump comprising a center rod capable of being driven to make a reciprocating motion relative to a main body block, in which a pair of diaphragms is secured to both ends of said center rod such that each of said pair of diaphragms may be located in place within head space so as to separate it to define a fluid delivering chamber and a driving chamber respectively. When the center rod is to be driven toward one side, a driving fluid (e.g., a compressed air) is supplied into the driving chamber located in an other side, an opposite side of said one side, of the center rod so as to discharge a fluid in the fluid delivering chamber located in said other side, and at the same time, the fluid is suctioned into the fluid delivering chamber located in said one side of the center rod while allowing the driving fluid in the driving chamber located in said one side to be exhausted, and when the center rod is to be driven toward said other side, the driving fluid is supplied into the driving chamber located in said one side of the center rod so as to discharge the fluid in the fluid delivering chamber located in said one side, and at the same time, the fluid is suctioned into the fluid delivering chamber located in said other side of the center rod while allowing the driving fluid in the driving chamber located in said other side to be exhausted, so that the fluid may be transferred continuously through this reciprocating motion of the center rod.
In this regard, said diaphragm-type pump comprises a pilot valve assembly block and a change-over valve assembly block, both of which are mounted on a main body block of the pump, said pilot valve assembly block including a pilot valve integrated therein as one body for detecting reciprocating strokes of the center rod and said change-over valve assembly block including a change-over valve integrated therein as one body for switching flow channels of the driving fluid based on a detection signal from the pilot valve.
However, in mounting operation of these valve assembly blocks, respective ports of the pilot valve assembly block must be positioned in proper locations with respect to respective ports of the change-over valve assembly block so as to form the flow channels for the driving fluid, and consequently this requires a certain level of machining precision for positioning the pilot valve assembly block relative to the main body block as well as the assembling precision therebetween.
Some diaphragm-type pumping apparatuses have employed an alternative configuration in which a positioning operation of the pilot valve assembly block relative to the main body block is not required in assembling therebetween but tubes for defining the flow channels are used so as to connect respective ports of the change-over valve assembly block with respective ports of the pilot valve assembly block, but this type of pumping apparatus could also lead to such an unfavorable situation owing to the tubes being laid externally, that the tubes may cause an interference with other structures located in the peripheral regions of the apparatus, and that in case of breakage or disconnection of the tube, the driving fluid could be leaked out.
This type of pumping apparatus also suffers from another problem that since the position of respective ports of the pilot valve assembly block is not fixedly defined relative to the respective ports of the change-over valve assembly block, the assembling location of the incorporated tubes is changed occasionally, which could produce undesirable variations in the performance of the diaphragm pump.
The present invention has been made in the light of the circumstances as described above, and an object thereof is to provide a reciprocating fluid transfer pump having such a configuration in which a pilot valve assembly block can be mounted to a main body block in a simple and easy manner without requiring a particularly high level of machining precision for positioning the pilot valve assembly block relative to the main body block.